B12-cell Division And Reproduction

Question 1

Chromosome

Answer 1

Long thread of condensed DNA

Question 2

Gene

Answer 2

Sections of a chromosome that carry specific information

Question 3

Alleles

Answer 3

Different versions of genes, specific characteristic

Question 4

Genotype

Answer 4

The specific combination of genes/alleles that an individual has is called their

Question 5

Phenotype

Answer 5

The physical presentation of the genes/alleles is called the

Question 6

Heterozygous

Answer 6

Different alleles one dominant and recessive(carrier)

Question 7

Homozygous

Answer 7

Same alleles can be both recessive or dominant

Question 8

In multicellular organisms

Answer 8

cell division (called mitosis) is needed for… replacing old cells and growing (repairing tissues as well)

Question 9

In unicellular organisms

Answer 9

this sort of cell division is needed for… asexual reproduction.

Question 10

Meiosis

Answer 10

Making eggs(and sperm)[gametes]for sexual reproduction

Question 11

Mitosis

Answer 11

Making identical 2

Question 12

What are the 2 different ways of reproducing

Answer 12

Asexual and sexual reproduction

Question 13

Asexual reproduction

Answer 13

only involves 1parent, cells divide MITOSIS gives rise to identical offspring or clone so genetic material is identical to parent and each other, cells of your body reproduce asexually all the time but very common in smallest animals and plant, and in fungi and bacteria also larger plants e.g.daffodils

Question 14

Sexual reproduction

Answer 14

involves 2 parents male and female sex cell these gametes fuse together to form a zygote to create a new individual formed special form cell division MEIOSIS each cell has half amount pf chromosomes so when formed has full amount so inherit genetic information from both parents which is key to long term survival and takes place living things ranging single celled organisms to humans in plants gametes=eggs+pollen in animals gametes=egg cell+sperm

Question 15

Fertilisation and variation

Answer 15

More variation is added when fertilisation takes place each sex cell has a single set of chromosomes(23) when joined the single new cell has a full set of chromosomes(46) the combination of genes on the chromosome of every newly fertilised egg is unique once complete it starts to divide by mitosis to form a new individual as number of cells increase rapidly and cells start to differentiate. In sexual reproduction by meiosis the combination of genes in the new pair of chromosomes will contain different forms of the same genes (alleles) from each parent. Unlike asexual reproduction by mitosis where there is no variation in genetic material.

Question 16

Meiosis steps

Answer 16

1. The cell contains pairs of chromosomes. In humans there are 46chromosomes(23pairs). 1 chromosome in each pair comes from the father and 1from the mother, each chromosome in the pair is the same length.
2. A copy is made of each chromosome. The original and the copy stay together.
3. The chromosome pairs line up down the centre of the cell. The pair from the father matches up with the corresponding pair from the mother.
4. The chromosome pairs separate and move to opposite ends of the cell. This is the same as a mitotic division resulting in 23pairs of chromosomes in each new nucleus.
5. The chromosome pairs now line up again in preparation for a second division. Their second division separates each original chromosome from its copy so that each new cell has 23 chromosomes. The new cells that form are called gametes.
6. 4new haploid cells are formed each containing 23 chromosomes. In males these are sperm and in females these are ova (eggs). Each new cell has a unique set of genes.
7. the sperm swims to the ovum and sperm’s head enters the ovum. The 2 nuclei merge to produce a fertilised egg containing 46chromosomes that can grow by mitotic division to form an embryo

Question 17

When does mitosis happen

Answer 17

This type of cell division occurs during growth and repair

Question 18

Where does mitosis happen

Answer 18

Takes place in all cells apart from gametes

Question 19

Mitosis how many cells

Answer 19

This type of cell division produces 2 daughter cells

Question 20

Mitosis how many chromosomes

Answer 20

The daughter cells have the same number of chromosomes as the parent

Question 21

Mitosis variation between cells

Answer 21

The daughter cells are clones and are genetically identical to the parent

Question 22

When does meiosis happen

Answer 22

This type of cell division occurs during the production of gametes (sex cells)

Question 23

Where does meiosis happen

Answer 23

This takes place in the reproductive organs

Question 24

Meiosis how many cells

Answer 24

This type of cell division produces 4 gametes

Question 25

Meiosis how many chromosomes

Answer 25

The daughter cells have half as many chromosomes as the parent

Question 26

Meiosis variation between cells

Answer 26

The daughter cells are genetically different from each other and the parent cell

Question 27

Info about mitosis

Answer 27

Chromosome replicate, which copies the genetic info
Produces genetically identical cells
2daughter cells produced
Occurs during growth and asexual reproduction
Only 1 cell division occurs

Question 28

Info about meiosis

Answer 28

4daughter cells produced
1copy of each chromosome (a chromatid)goes to each of the new daughter cells
Occurs in the formation of gametes during sexual reproduction
Only 1/2 of the chromosomes go to each of the new daughter cells
Daughter cells are all genetically different
2 cell division occur

Question 29

Process when 2 human gametes join together

Answer 29

Fertilisation

Question 30

The human genome project

Answer 30

was one of the major biological programmes of the
last 20 years. At the outset biologists believed that sequencing all human genes
could provide answers to many questions, such as the causes of some diseases
and the origin of some species

Question 31

What is a genome

Answer 31

The entire genetic material of the organism

Question 32

In 1990s biologists started the human genome project the aim was

Answer 32

To sequence a genome of a person

Question 33

How has the human genome project been extended

Answer 33

Since the initial human genome was read scientists have carried on with the work and the aim is to find out as much as possible about human DNA. As they have now sequenced the genomes of 1000people and are now busy with the current 100,000 genomes projects and even other organisms. Because there is still a lot to find out and there are many reasons why they feel it is worthwhile like understanding inherited diseases more.

Question 34

advantages of the scientists being organised into teams

around the world to work on the human genome project.

Answer 34

It means that thousands of people all across the world are experimenting and working together for the same goal with different people doing different things.

Question 35

how scientists used genome sequencing techniques (such as the
human genome project) to establish a classification relationship between two
species.

Answer 35

Because they sequence genomes of hundreds of different species of organisms and use the similarities and differences between two species to help them work out the relationship between the two different species.

Question 36

The benefits of the human genome project

Answer 36

Understand inherited disorders so the more chance of overcoming through medicines or repairing the faulty genes, the more we likely we are to predict the risk for an individual so they can make lifestyle choices to reduce this risks and finding the best treatment for things like cancer and human evolution and history to trace migration patterns from our ancient history and early members of the human family tree.

Question 37

A capital letter is always used to refer to the

Answer 37

‘Dominant allele’

Question 38

A lower case letter refers to the

Answer 38

‘Recessive’ allele

Question 39

Genetic screening

Answer 39

Cells can be taken from an embryo/foetus and tested or ‘screened.’
These processes check for alleles that cause genetic disorders.
This can be ‘pre-implantation’by screening embryos for faulty alleles during IVF, or it can be post-implantation (e.g.amniocentesis)

Question 40

What is amniocentesis

Answer 40

Involves taking some fluid from around the developing fetus at around 15-16weeks of pregnancy this fluid contains fetal cells, which can then be used for genetic screening

Question 41

How are amniocentesis and chorionic villus sampling similar

Answer 41

They both have a risk of a miscarriage but are currently the 2 main methods used to obtain fetal cells for screening which they both do as well

Question 42

What is chorionic villus sampling

Answer 42

Involves taking a small sample of tissue from the developing placenta earlier between 10 and 12weeks this again provides fetal cells to screen

Question 43

advantages and disadvantages to offering embryo screening to all pregnant couples:

Answer 43

Although screening is very expensive if a couple have a child affected by a genetic disorder it can be very costly for society to provide health care. But it helps the parents to be prepared because if they are going to have a child with a genetic disorder at least they would know how to get prepared for it and it wouldn’t be a shock. They can also make the choice whether or not to terminate a pregnancy although this is never an easy decision it will have a huge impact on their lives and if they are young especially this will affect them a lot and it may cause ‘too’ much suffering to a life ‘not worth’ living. Some people also are concerned that genetic screening would give rise for ‘designer babies’ with desirable attributes instead of having a normal baby. Also their are risks associated as the processes used to collect cells from a developing fetus increase the risk of miscarriage and screening procedure although they are becoming more reliable and accurate they can give a false positive or false negative result leading to a healthy fetus being miscarried, the termination of a healthy pregnancy or unexpected birth of a child with a genetic disorder.